I think the reason IHT is so hated is because you're stealing from our kids.
Some taxes have a hugely disproportionate negative effect because they're not just about the money, they also change the way we understand our relationship with society: how we and our family fit in and what we can expect.
We're used to you stealing from us with redistributive taxation, and have absorbed the idea that 'we'll cope'.
It's annoying when you declare that the things our money pays for is only for other people, and we don't get to share the supposedly 'universal' services. That stings. When our generosity isn't reciprocated, it puts the whole 'support other people because you're part of a society' assumption into question. Means testing the state pension would be incredibly socially destructive because of this.
But when you stand between us and our children, and steal what we're trying to give them, that raises a protective anger which you underestimate at your peril.
The same protectiveness is behind the huge anger at private school VAT. I think Labour still have no idea what they've done. If society shows me that it doesn't value my child, that it will steal from her at every opportunity - rather than support and help her - it's worth nothing to me.